Are they? A lot of them surely are, but there are also people (including writers) who are drawn to characters with a long history, a rich legacy, and sometimes also a high status. Or as G Willow Wilson said about being offered the chance for writing Wonder Woman:
So it really did seem like the right place, the right time. And even if it hadn’t been, when you get a call saying, “Hey, can you write Wonder Woman?” You don’t say no. You find a way, you find the time. I was very honored to be asked.